KAP100 Dilemma

[Txbyker]

Guys I wonder if anyone can help me with a KAP 100 autopilot question.  I am trying to finish up my instrument ticket in my M20J which I have owned a few months.  It has a KAP 100 autopilot working with a KLN94.  I plan to go to the GTN soon but want to get the IFR out of the way before the 3-4 week downtime for new avionics (and interior).

My KAP seems to fly through the intersections and not aggressively grab the new track.  I say aggressively because if for example I start out in HDG mode and change to NAV, turn the heading bug to the new CDI course it will roll towards the new course and eventually come close to tracking the new course after shooting past the desired track.  Then in about 1 degree every 4-5 seconds it will creep back to the desired track.

I have to fly a GPS approach with autopilot for my checkride.  When in APR mode it flies right past the turn. HDG bug works fine by the way.

I have some choices, have a mechanic disable and mark the autopilot disabled, fix the autopilot, or put it in the shop for avionics upgrades for a month.

Has anyone had issues like this with their KAP 100?  Hopefully it is something simple.

Thanks,

Russ

[LFOD]

We have another thread going about auto pilot woes. Unfortunately, it is never simple when it comes to these things.  Just bite the bullet and have an avionics guy look at, but I would suggest doing it after your checkride. Placard it inop and drive on with your training.  Good luck!

[kortopates]

Quote: txbyker

My KAP seems to fly through the intersections and not aggressively grab the new track.  I say aggressively because if for example I start out in HDG mode and change to NAV, turn the heading bug to the new CDI course it will roll towards the new course and eventually come close to tracking the new course after shooting past the desired track.  Then in about 1 degree every 4-5 seconds it will creep back to the desired track.

I have to fly a GPS approach with autopilot for my checkride.  When in APR mode it flies right past the turn. HDG bug works fine by the way.

From the description its a bit difficult to tell if you are indeed turning the Course knob/OBS on the CDI, when in NAV mode, to the desired new course as the GPS sequences to the next waypoint. Changing the Heading, of course does nothing when in NAV mode. Could this be why "in APR mode it flies right past the turn".  

Perhaps its worthwhile to review how to properly enter Approach mode so you can verify its not an operator issue and a AP issue. (This all assumes you don't have an additional GPSS capability between the GPS and AP, which I could be wrong but don't think is supported by your KLN94 and you make no mention of GPSS.)  The standard KAP 150 uses the KG107 and second CDI but may have the optional KI 525A HSI combing the two. I'll assume the KG107.

First, the approach mode is not armed till you are intercepting the final approach course. While in heading mode, and on a heading to intercept the final approach course, place the OBS of the CDI set on the final approach course. Then press APR and it will blink indicating it is armed. Within 5 seconds, move the heading "bug" of the KG107 to the same heading as the selected course of on the CDI. The autopilot will fly an automatic 45 degree intercept heading until within the capture zone, then intercept and fly the desired course with the HDG light going off  and the APR mode goes from arm to engage. If APR mode is selected within +/- 4 degrees and withn 2-3 dots on the CDI the ARM mode is bypassed and APR mode will engage directly. There are many more complicated scenarios in your King AP manual to review, such as approaches with course reversals and Back Course, but I wouldn't assume an AP issue till you verified its not working following the above simple intercept procedure, taken from your AP manual. Enjoy and good luck with your IFR training.

[Txbyker]

Thanks Paul.  Yes I have a KG107 with heading bug and two KX155 for CDI.  The top KX155 is an ILS and the bottom is a VOR/LOC.  The CDI on the bottom (VOR/LOC) is the one to use in GPS mode.

I can be flying in heading mode while setting the GPS in the KLN94.  Then press NAV and adjust the KX155 CDI to the new desired track. Then within 5 seconds I adjust the heading bug on the KG107 to match the CDI.  The plane will steer to the new CDI/Heading and go past it about 10-15 degrees.  Then it will slowly, very slowly attempt to fly back to the CDI/Heading about 1 degree every 4-5 seconds.

Last night I set up a GPS approach, got ATC cleared to the first point.  I had the GPS approach loaded, pressed NAV, moved the CDI to the desired track and set the heading bug on the CDI course.  The plane turned toward the new heading and blew past the first GPS approach point.

My IFR instructor has many hours with the KAP100 and KLN and thinks there is something wrong with the unit.

I think it must be something between the KX155, the KAP100 and the KLN94 not reading the DTK.

I am going to label it in-op I think.

Thanks!

[kortopates]

Concur that it shouldn't be going past the current Heading bug value - if when you've come to the desired heading you're GPS and CDI is not indicating a major deflection - more than a couple dots. In other words, if the plane is not on the desired GPS Track when it completes the turn to the desired course it wouldn't be abnormal for the AP to have to continue the turn to correct for being offset from the desired Track. 

Quote: txbyker

Last night I set up a GPS approach, got ATC cleared to the first point.  I had the GPS approach loaded, pressed NAV, moved the CDI to the desired track and set the heading bug on the CDI course.  The plane turned toward the new heading and blew past the first GPS approach point.

[carusoam]

From my KAP 150 and KLN90B experience.  I have had similar issues while learning the system....

The KLN90B has turn anticipation, I would expect the 94 does also...

Keep in mind there are two types of GPS way points, fly over and fly by. 

The GPS can sequence to the next waypoint when you are close.   As the pilot fiddles, twists and gets the timing wrong, the plane seems to take an incredibly long period of time to go back on course.  90 degree turns, would be the worst case.  Of course the AP doesn't just go direct, it goes back and intercepts the course that is originally selected.

I recommend some practice runs at first.  String a few VOR way points together.  Do it with the nav radio as the source one time and the GPS as the source the next.  The GPS will fly in straighter lines.  The VOR should fly a more scallopped pattern. 

When the GPS is the source, there should be a blue light on indicating the switches are set correctly.  When no light is on.....well it doesn't mean anything....  How does the AP know what source (GPS vs NAV) you want to use?

I found getting the source set up properly, selecting that source for navigation, and pushing the correct buttons on the AP to be exasperatingly challenging at first....

Then compare obs mode, leg mode, direct, and then finally add the approaches...

Check your DG for accuracy.  If the DG is wandering off course, the AP calculations seem to wander also.......?

Of course, pick a nice sunny day with good visibility.  You will have your head down in the cockpit, so expect to bring someone along, or be extremely vigilant not to be looking down....

Best regards,

-a-

[Txbyker]

OK, bear in mind I have been training a long time in a G1000 and am learning the KLN and KAP...so here goes a stupid question.  When in NAV mode and you transition from point A to point B and the KLN is flashing its turn anticipation at you is the pilot suppose to realign the CDI to the new course and turn the bug to the new course?  So basically the KAP 100 keeps you tracking straight on a heading but you must manipulate the turns through the heading bug?  (if the answer is yes, perhaps this should have been a private message)

Thanks

[kortopates]

Yes - this was my questions to you in my first post - you have to be updating the OBS on the CDI as you sequence through waypoints in your GPS while in NAV mode. Do it when your GPS provides the turn anticipation but if it just provides a fixed 35 sec warning, then you have to estimate (i.e. 10 sec for 30 degree intercept). Turning the Heading bug while in Nav mode doesn't do anything. But note if you are peforming VOR navigation, then you KFC manual tells you switch to use HDG mode just as you approach the VOR and to turn to the new heading and course and then set the new course into your OBS of the CDI and switch back to NAV mode once your past the zone of confusion right over the VOR.  

Your installation must have GPSS capability before you no longer need to keep updating the OBS on the CDI to follow a series of waypiint in NAV mode.

[carusoam]

txb...

Unlike a G1000 with gpss, you (the pilot) are still required to help fly the plane.   (this is good news for most of us).

With the KAP 150 in Nav mode, we have to be ready with the next heading/course in hand.  when the light starts to flash, adjust the OBS to the new heading.  When the light is steady the time for anticipation is gone.....

I use the heading bug in advance to remember what the new course will be.  The system will keep flying the original course until you give it the new one.   I do not use the heading mode of the AP unless ATC is giving me headings.

If you were to fail to put the new OBS course in properly, the KLN will let you know with a message that says adjust desired track to XXX.

When everything is working correctly, you can compare desired track to actual track and they should be very close.  minor adjustments to the OBS will give you spot on results comparing ATK to DTK.

Again, this is KAP150 and KLN90B experience.  KLN94 is very similar to KLN90B (accept color screen and menu structure). 

I am not specifically familiar with the KAP100,  One of the updates for the KAP150 includes using the heading bug to set the intercept course.

The challenge for the pilot new to this system is as follows:  you are blissfully flying along and waiting for the plane to turn on the next way point.  Unfortunately, the only hint that it is time to turn, is the countdown timer to the next waypoint and a small flashing light, followed by ATC asking "ummmm, N201XX are you still on victor YY?"

you will also be challenged in a similar fashion with altitude changes.  How do you remember to level off after a 10,000 foot change in altitiude?  ATC will use the phrase "N201XX can you state your altitude?"

Best regards,

-a-

[kortopates]

An update to my prior post. I found a KLN94 Users Guide and found Turn Anticipation is an available feature that must be Enabled. So check Set up page 10 to verify Turn Anticipation is Enabled (or see page 4-10 of you manual) . With it enabled it behaves a bit differently from what carusoam described above. When the WPT annunciator in the upper right section of the screen begins to flash, this is Waypoint Alterting (Not turn aniticpation), more precisely its a 20 second alert to Turn Anticipation. Turn Anticipation begins when the Waypoint flashing goes to a solid from blinking and the unit tells you the new course to dial in - now turn the OBS on the CDI to initiate the turn. If you don't have turn anticipation turned on, then you'll get a 36 sec (not 35 sec as I recalled earlier) altering/blinking message all the way to station passage. So ensure its enabled.

Hope that helps. 

[Txbyker]

Thanks everyone.  I am new at this and didnt realize GPSS is missing.  I will give this a new try tomorrow.

Russ